I didn't take my cat to Southern Ag when I had him snipped but I dropped him off around 8am and picked him up after recovery at 1:30pm. I'm sure it varies based on quite a few factors but plan for the day.
I'm not a veterinarian, but I imagine the process takes about an hour and then recovery so either you would drop him off in the morning and pick him up in the evening or he would spend overnight.
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